even though nolan is against the idea, it would be very logical for robin to show up in number three. batman's failure to save either long-distance love rachel dawes or crusading "white knight" harvey dent, even with the help of commissioner gordon and the gotham police force, would make batman very interested in finding a reliable partner with special skills more like his own.

it would also be logical for catwoman to show up. her skills would make batman interested in recruiting her as well — if he could figure out if she's truly bad or could be turned to good. but he'd also be forced to question his motives in pursuing her, since the loss of rachel must leave him emotionally vulnerable. a possible subplot could follow a rivalry between robin and catwoman for batman's attention.

but even if catwoman ended up as one of the bad guys, she doesn't have the threat-level to carry the film as the main villain. both batman begins' ras al ghul and the dark knight's joker took the city to the brink of destruction; catwoman simply isn't that menacing.

despite much gossip about the riddler, he's always seemed too much like a poor man's joker to play second act to the real thing, especially on the heels of heath ledger's daunting performance. like catwoman, the riddler's never been an existential threat to gotham city. unfortunately, despite seventy years of adventures, batman's arch-enemies a-list is surprisingly short and nolan has been going through it two at a time, while rightly disqualifying villains like the penguin and mr. freeze as too outlandish.

it's a tall order to fill: enough gravitas to have been a major batman villain and enough menace to terrorize the entire city, yet enough plausibility to exist in nolan's gritty and realistic universe. even as a life-long batman fan i'm stumped and the only name that springs to mind is dr. hugo strange but even he might not be good bad enough.